244. GENERAL. Glen Canyon Switchyard (figure 216) is located on the right canyon rim starting about 600 feet downstream and 700 feet above the powerplant, within a fenced area approximately 800 feet by 1,200 feet. Seven of the eight transformer circuit towers for the powerplant to switchyard transformer circuits are located inside this fenced area, between the switchyard and the canyon rim. The other transformer circuit tower and a ground wire mast are located on the left canyon rim across from the switchyard. An access road was constructed from U.S. Highway No. 89 to the entrance at the northwest end of the switchyard, and a parking area was constructed at the entrance outside of the fenced area. The high-voltage switching and termination facilities located in the switchyard are described in Chapter IX.

An inclined tunnel was constructed from the powerplant to the switchyard, primarily for use as a control cable duct. This tunnel is about 7 feet square and 1,300 feet in length. A shallow type C cable trench extends from the powerplant control cable tunnel entry structure the entire length of the yard with a branch trench into the 25-kilovolt area. Control and power cables are buried from the cable trench to all equipment.

All electrical equipment for the switchyard was furnished by the Government. All other materials, including steel structures, overhead conductors, hardware, insulators, and control and power cables were contractor furnished. Initial excavation and grading was performed by the prime contractor under specifications No. DC-4825. The construction of the major portion of the switchyard was accomplished under the completion contract, specifications No. DC-5750. The 59-kilovolt facilities and the microwave power supply were constructed under specifications No. DC-6238 and the 5-kilovolt visitor center bay under specifications No. DC-6274. The effect of the expedited completion schedule for specifications No. DC-5750 was quite pronounced, since large areas of the switchyard were behind the original schedule at the start of the expedited program.

containing an area of approximately 5.1 acres, and was surfaced with 6 inches of gravel surfacing. Owing to changed requirements of the present and future number of transmission lines and voltages to be provided, the switchyard was enlarged by the completion contractor to an irregular shape with maximum dimensions of 476 by 1,196 feet and the yard was lowered 1 foot at centerline, more than doubling the size to approximately 11.5 acres. Most of the gravel surfacing placed by the prime contractor was salvaged and stockpiled prior to initiating grading for the enlarged switchyard. The switchyard was graded using conventional methods and equipment in the excavated sandstone and blowsand. Much of the excavated sandstone broke down into an unsuitable, uniform-grained sand, which had to be wasted by the completion contractor. Compaction of the embankment was by equipment travel and vibratory-type compactors.

Grading for the switchyard and structure foundation construction was subcontracted to Fago Brothers Construction Co. of Scottsdale, Ariz. Work began on the grading phase early in July 1962 and the general grading had been essentially completed by the end of the year, except for the area adjacent to the control cable tunnel entrance structure. Work in this area was completed after the entry structure concrete was completed in July 1964. The salvaged gravel surfacing was spread, plus additional gravel, to stabilize the switchyard surface for access during the foundation construction phase. Order for changes No. 1 also provided for a 12-inch blanket of pit-run gravel on the switchyard embankments for erosion control. No drainage collection system was provided on the canyon side, and repair of this gravel blanket is necessary after occasional heavy rainstorms. A curb and outfall line system was planned for construction among future completion items. The switchyard access road and parking area embankments and bituminous surfacing were completed in October of 1964. The switchyard gravel surfacing was completed during October of 1966 and application of soil sterilant followed.

Most of the concrete foundations for the switchyard structures were designed for either pad- or rock-type foundations. The type of foundation used for the various structures was determined by the type and quality of material encountered. Concrete for the switchyard foundations was batched at the completion contractor's batching plant, located near the upper

portal of the powerplant access tunnel, and was delivered to the switchyard by transit mixer. Conventional practices were followed in constructing the wooden forms and placing reinforcing steel and concrete for the structures and with curing of concrete by membrane curing compound.

The batching plant at the tunnel portal was provided by the subcontractor on the powerplant concrete. At times it was difficult to obtain concrete for the switchyard due to the heavy demands by the powerplant subcontractor. Placement of switchyard concrete foundations began during April 1963, and after changes in subcontractors was completed in November 1963 by the prime contractor, Ets-Hokin Corp. The remaining switchyard concrete, including conduit encasement, pullboxes, cable trench, cable trench crossings, and switch operating platform supports, was completed by the end of July 1964. To provide for temporary 230-kilovolt operation of the 345-kilovolt Flagstaff transmission line No. 1, additional structure foundations were constructed by the completion contractor in November 1964 as provided for by order for changes No. 5.

Structural steel for the switchyard was furnished by Muskogee Iron Works of Muskogee, Okla., and erection was performed by the completion contractor. Switchyard steel was assembled on the ground with loose-bolted connections. The larger structures were assembled in box sections on the ground. After erecting with mobile cranes, the structures were plumbed and all connections torqued. No unusual difficulties were encountered, although some misfabricated members required replacement or reworking. When holes were required to be redrilled or repunched, the galvanizing was repaired using zinc dust-zinc oxide priming paint. Erection of the switchyard structural steel began in the 25-kilovolt yard during August 1963, the 345-kilovolt yard during mid-September, and the 230-kilovolt yard during the last part of October. At the end of the year, all major steel structures in the switchyard had been erected.

246. HIGH-VOLTAGE BUSES. The east and west 345-kilovolt buses are 954,000-circular-mil all-aluminum duplex strain type, and taps from the bus to switches and jumpers between disconnects and breakers are also duplex cable. The connection of unit 5 to the west bus is accomplished with 3-inch iron-pipe-size aluminum rigid pipe welded to form a continuous length. Bus support clamps and connectors are of the bolted type. Corona-free hardware was installed on all 345-kilovolt bus, and corona control

rings were used with all compression dead-end assemblies. Particular care was taken to avoid abrasion or contamination of the stranded cable in order to minimize corona.

The 230-kilovolt bus is also a combination of strain and ground mounted rigid 3-inch aluminum pipe bus. Conventional compression fittings and hardware and bolted fittings are utilized. The strain bus and jumpers are single-conductor, 1,272,000-circular-mil all aluminum. In order to dampen vibrations in long lengths of rigid pipe bus, 1,272,000-circular-mil stranded cable was inserted in the full length of the pipe.

is

The 25-kilovolt strain bus for the tertiary of the 345- to 230-kilovolt autotransformer 2,500,000-circular-mil all-aluminum with compression dead-end assemblies. Taps to the bus are made with bolted connectors. All other 25-kilovolt strain bus, between the pothead structure and the switch structures, and jumpers from the buses to disconnects and circuit breakers are 1,272,000-circular-mil all aluminum. The main and transfer buses are 2-inch iron-pipe-size aluminum pipe as are connections between line and bypass disconnects. The contractor experienced considerable difficulty in producing the uniform short-radius bends which were necessary in this bus.

The 25- to 69-kilovolt transformer circuit is 954,000-circular-mil all-aluminum cable installed with compression dead-end assemblies. Essentially all other 69-kilovolt bus work is 2-inch iron-pipe-size aluminum pipe supported by post-type insulators.

All bolted taps and connectors to the various buses were made up with torque wrenches in accordance with the recommendations of the hardware manufacturer. Close inspection was maintained to assure that the aluminum conductors were properly cleaned prior to making up connections.

In order to temporarily utilize the 345-kilovolt Flagstaff line at 230 kilovolts as an interconnection to Arizona Public Service Co., a tie circuit between the 230-kilovolt west bus and the 345-kilovolt west bus was installed under a change order on the completion contract.

This temporary tie was utilized from December 1964, through October 2, 1965. A second temporary bus connection tying the 230-kilovolt east bus to the 345-kilovolt west bus was installed by Government forces using live-line bare-hand techniques, in April

1965. The temporary connection to the 230-kilovolt west bus was removed at that time.

247. TRANSFORMER CIRCUITS. Four transformer circuits were constructed from the powerplant takeoff to the switchyard takeoff structures. Circuits No. 1 through 3 are designed for operation at 345-kilovolts and circuit No. 4 at a voltage of 230 kilovolts. In order to provide the required clearances for the four transformer circuits, it was necessary to excavate 3,475 cubic yards of rock at the canyon rim. This work was provided for by order for changes No. 5 and was accomplished by the prime contractor under specifications No. DC-4825. The work started late in November 1960 and continued intermittently until completion in March of 1961.

The completion contractor under specifications No. DC-5750 was required to construct the transformer circuits including furnishing and erecting the takeoff structure at the powerplant and the tower structures, and furnishing and stringing the required conductors, insulators, and hardware. Before work could begin on the west rim structures, it was necessary for the subcontractor to salvage and remove the temporary visitors' parking area and overlook facilities. Work began early in August 1962, and the tower footings were excavated in conjunction with construction work for the switchyard. Foundations for the transformer circuit towers were constructed in rock in accordance with the construction drawings. The foundation outlines were line drilled and the material was loosened by shooting with 60 percent powder. Placement of foundation concrete began during February 1963 and was completed in October of 1963.

and

The transformer circuit rim towers were fabricated from extra-high-strength, high-strength, standard-strength steels. The higher strength steel members were furnished painted with zinc dust-zinc oxide paint and the standard steel members were galvanized after fabrication. The remaining towers were fabricated with standard steel galvanized after fabrication. A hydraulic crane with a telescoping boom was used in the assembly of the tower sections on the ground. A 60-ton mobile truck crane with full boom and jib was used to erect the tower structural steel. To provide the reach for erecting the west side rim towers, it was necessary to construct temporary embankment pads adjacent to each tower. These embankments were later removed and the area dressed. The tower sections were assembled with loose bolts and, after erection and plumbing the bolted connections were torqued as required for the various bolt sizes.

The structural steel for the transformer circuit towers was also furnished by Muskogee Iron Works of Muskogee, Okla. Some fabrication errors required repunching and redrilling by the erectors. Resulting injuries to galvanized or paint coatings were repaired using zinc dust-zinc oxide priming paint. Erection of the transformer circuit steel towers began during December 1963, and by the middle of June 1964, was essentially completed.

Stringing and sagging of the transformer circuits was accomplished during late spring and summer of 1964 by the contractor's line crew and equipment being used on the construction of the 345-kilovolt Glen Canyon-Flagstaff transmission line No. 1 under another contract. Circuits No. 1, 2, and 3 were 2,167,000-circular-mil ACSR (aluminum conductor, steel reinforced) conductor, Circuit No. 4 was 954,000-circular-mil ACSR conductor and the overhead ground wires were 1/2-inch galvanized steel cable.

Stringing was done from the transformer deck to the rim towers, and the spans were attached to the towers with double sets of tension insulator strings. Hot-line hardware was used on the switchyard spans, along with corona rings and corona-free fittings in the high-voltage circuits.

248. CONTROL CABLE TUNNEL. The control cable tunnel extends from the powerplant on a 7- by 7-foot section approximately 1,300 feet long excavated in the canyon rock on a slope of 29°32', terminating with concrete entrance structures. The upper portal is at the north end of the switchyard; the lower portal connects to the powerplant cable tower with a bridge section 53.5 feet long. The control cable tunnel serves as a duct for switchyard control cables, ground wires, communication cables, and a 25-kilovolt auxiliary power supply cable from the switchyard. The tunnel was constructed with galvanized cable trays, steel stairs, and a lighting system.

Excavation for the control cable tunnel, provided for under the prime contract, specifications No. DC-4825, was subcontracted to Frazier-Davis Construction Co., who in turn subcontracted the excavation to Cannon Diamond Drilling Co., of Compton, Calif. Work began with an opencut section in the switchyard area during September 1957, and was holed through into the canyon, approximately 100 feet above the river during March of 1958. A track-mounted, pneumatic overhead mucker was used to load the loosened material into a cable-hoisted muck

car for hauling to the upper portal area. The excavated material was dumped into trucks and was wasted. Jack-leg drills were used to drill the powder holes, and about 10 feet of tunnel was excavated each two-shift day.

During January and February of 1963, the lower portal and portal invert concrete was placed by the prime contractor. The control cable duct between the tunnel and powerplant was a structural steel truss bridge, 52 feet 8 inches center-to-center bearing, with insulated metal wall panels and an open steel grating floor. Assembled at one of the rim storage yards, the bridge was set in place on the bearing plates early in April of 1963, using one of the 50-ton high-line cableways. Late in April, the pitched reinforced concrete roof was cast in place on the bridge.

Work performed by the completion contractor on the control cable tunnel included placing concrete for the tunnel walls arch and upper entrance structure, furnishing and installing the steel stairs, cable trays, and completing the required electrical installations.

Concrete for the control cable tunnel was batched at the upper portal area using a skip-loading mixer and a wheelbarrow scale. A specially built rubber-tired car, operated by a cable hoist at the upper portal, was built to transport materials, men, and equipment to the work area in the tunnel. The contractor excavated rock for the wall keys and placed concrete for an enlarged curb to support the wooden wall forms and provide a track for the access car. The enlarged curb concrete was placed beginning in early October 1963 and was completed in early December. Both sides of the wall concrete were placed simultaneously from the bottom between January and March 1964.

Conventional arch concrete was placed during April and May 1964 to the A-joint crossing. The A-joint was left unlined 15 inches on each side except where concrete inserts were required to be installed in the walls. From the joint to the transition to the entrance concrete, the arch was lined with 4 inches of pneumatically applied mortar, which was reinforced with welded wire fabric. Subcontracted to the American Gunite Co. of Salt Lake City, Utah, arch mortar was placed in two 2-inch passes during May of 1964. Concrete for the entry structure was placed during July of 1964.

Installation of the steel stairs and cable trays began in early June from the lower portal of the tunnel and was completed on the downstream side by mid-July. Pulling of control cables under the expedited program

schedule followed and was completed by the end of July with installation of the remaining cable trays and cables later.

Techni-Builder, Inc., of Phoenix, Ariz., was awarded a contract under specifications No. DC-6351 (SF) to furnish and install a handrail on one side of the control cable tunnel stairway and to furnish and install chain-link, mesh-covered, safety gates on approximately 25-foot spacings throughout the length of the stairway. Installation was started December 6, 1965, and was completed December 10, 1965.

249. MINOR ADDITIONS. The 69- and 2.4-kilovolt microwave power supply additions to the Glen Canyon Switchyard were constructed under specifications No. DC-6238. Tide-Bay, Inc., of Tacoma, Wash., was awarded a contract for the work under these specifications and began work June 7, 1965. All work was completed December 4, 1965. The switchyard area had been graded, surfaced with 6 inches of gravel surfacing, and fenced by others under specifications No. DC-5750, prior to work under specifications No. DC-6238.

Reinforced concrete foundations were constructed for a 69-kilovolt power transformer, a 25-kilovolt transformer circuit tower, and a 69-kilovolt transformer structure, all in the 69- to 25-kilovolt transformer area of the switchyard. In the 69-kilovolt area, concrete foundations were also constructed for a bus structure, a circuit breaker, a current transformer support, and a potential transformer support, all 69-kilovolt, as well as a microwave supply terminal structure. Four reinforced concrete 69-kilovolt approach tower footings were constructed at P.I. station 1+98.8 of the Glen Canyon-Page 69-kilovolt transmission line.

Both the 69- to 25-kilovolt and the 69-kilovolt areas were located at the north end of the Glen Canyon Switchyard. Structural-steel structures furnished and erected under this addition included two bays of 69-kilovolt bus structure, one transformer structure, one potential transformer support, two current transformer supports, one approach tower, all 69-kilovolt; one 25-kilovolt transformer circuit tower, and one microwave supply terminal structure. Also included were field alterations to an existing 25-kilovolt fuse and bus support, field alterations to a 25-kilovolt bus structure, and furnishing and installing switch-operating platforms. Transformers, circuit breakers, and switches used in this modification and addition were Government-furnished.

Other major items installed or furnished and installed included various sizes of exposed electrical rigid metal conduit; nonmetallic conduit embedded in concrete; lightning arrestors and grounding systems; aluminum strain and jumper buses; rigid aluminum buses; bus supporting insulator assemblies; outdoor bracket-type lighting units; terminal boxes; two 69-kilovolt approach spans of 69-kilovolt transmission line complete with conductors and overhead ground wires; and one span of the microwave two-wire power supply line.

Provision for removing and restringing one span of messenger-supported communication cable in the switchyard was deleted from the specifications requirements and was handled by operation and maintenance personnel to minimize communications interruptions. Other minor modifications and additions were made to the Glen Canyon Switchyard under specifications No. DC-6274, to supply electrical power to the visitor center at Glen Canyon Dam. These involved constructing reinforced concrete foundations for a 5-kilovolt bus structure and a 1,500-kv-a. transformer; installing a 22,900- to 2,400-volt, 1,500-kv.-a., 3-phase transformer; and furnishing and erecting a 5-kilovolt bus structure complete with disconnecting fuses, lightning arresters, rigid aluminum bus, insulator assemblies, and grounding system. The power is transmitted to the visitor center through a concrete-encased buried duct bank. A lateral off the main duct bank was constructed to a dead end near the upstream side of the west abutment of the Glen Canyon Bridge to provide for future requirements.

A. SWITCHYARD ELECTRICAL

EQUIPMENT

250. GENERAL. All major switchyard equipment was furnished by the Government and with few exceptions was delivered to the completion contractor at the railhead in Flagstaff and trucked to the site as provided in the specifications. All of the equipment was at the site sufficiently in advance of dates required to allow an orderly equipment installation program.

251. AUTOTRANSFORMERS. Three 100,000-kv.-a., 345-230-25-kilovolt autotransformers were furnished by Westinghouse Electric Corp., under invitation No. DS-5784. The original scheduled shipping date for the units was August 1963. However, all three transformers failed during impulse testing at the factory and were rejected. The transformers were rebuilt, successfully tested, and shipped in March 1964, arriving at the railhead in Flagstaff on April 6.

The transformers were hauled by the completion contractor's hauling subcontractor, Reliance Trucking, to the switchyard and set on their foundations on April 14 and 16, 1964. Assembly of the transformers under the supervision of the manufacturer's erecting engineer began May 12, 1964. Two of the transformers were found to have suffered shipping damage to the bushing current transformers on the high-voltage bushing, caused by failure of the current transformer support arrangement. Assembly and checkout of the undamaged unit was completed on May 25.

Repair and replacement parts were ordered immediately for the damaged units. It was found that the transformer manhole was not large enough to permit removal or reinstallation of the bushing current transformers. Modification and enlargement of the manhole was accomplished as a part of the repair procedure. The necessary parts arrived June 26 and installation was completed July 8. Normal assembly procedure of the two transformers was then continued and was completed July 16. Doble testing of the transformer bushing revealed one bushing which had an open capacitance tap. This bushing was removed and replaced with a bushing intended for transformer K7A. A new bushing was shipped from the factory on July 30 for subsequent installation in transformer K7A.